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Cozy MKIV - Sixteenth Flight Test

Date: September 14, 2002

Saturday morning I headed out to the airport bright and early, and actually got there around 830 AM. Fitchburg is having an "Airfest" this weekend, and the airport was closing at 130 till 430, so I wanted to get my flight in early.

I ballasted the plane for 1900 lb. rear CG (102"), which entailed 10 lb. in the front seat with me, and 200 lb. in the back seat, along with 58 - 60 gallons of fuel. I decided to do an easy, relaxing day to put a few hours on, so I programmed the GPS for a zig-zag flight over most of the airports in central/western MA. I wanted to test the GPS/Navaid Coupler at waypoints with large turning angles, as well. I also thought that I would do some preliminary stability and flutter testing, as I was cruising along. I flew out over Orange, then north to Keene, then SW to Turner's Falls, then West to Pittsfield.

I landed there (why do people think it's an OK thing to ask you questions on the radio [like, hey, George, is that you in the COZY?] when you're on short final?. I'll be happy to answer questions after the wheels touch.....) and then headed off toward Northampton and Windham, CT. Then, back up into MA, around Worcester Class D, and back to FIT, where some dingus in a Mooney decided to cut me off on downwind, and then climb out of the pattern. I have no clue what he was thinking.

At any rate, along the way I used the handy dandy capabilities of the Garmin 195 to calculate my TAS. At 6500 ft and about 50 degrees F, I was indicating 175 mph at 2700 RPM, which trued out to 194 mph. Geez, that's pretty good for a plane with no spinner or wheelpants.

Along the way, I decided to do some pitch stability tests. Once I was at a stable speed, I would push on the stick and stabilize at a speed 5 mph faster or 5 mph slower than I had trimmed to, and then release the stick. I'd wait and see how the nose would oscillate up and down, and whether it would return to the trimmed airspeed. For the couple of speeds I tried around 150 - 160 mph indicated, three or four oscillations would return the plane to trimmed speed, over the course of a minute or so (nothing scientific here yet - that'll come later).

I also did some flutter tests, both in pitch and roll. At 170 and 175 mph indicated, I whacked (that's the technical engineering term for an extremely controlled force input) the stick in all four directions (independently, not all at once). The idea here is to see if the "whack" will excite vibrations in the corresponding control surface. In all cases, there were NO extended vibrations of the control surface - the surface almost immediately returned to it's trimmed position. I will say, it's a bit weird to stare at the elevator at 175 mph (194 true) and whack the stick, feel the plane rumble up and down a bit, see the elevator move up and down once and then stop moving as if nothing had happened.

A few other random observations. It was very calm - no turbulence at all, and the pitch trim system held altitude extremely well - there were minutes at a time where the altitude didn't vary by 20 feet. Because my course was such a zig-zag, some of the waypoints had large angular turns at them, from 90 degrees to 160 degrees. The GPS notified me that I had "STEEP TURNS" coming up at the next waypoint. The "smart coupler" did a good job of staying on course when the turn angles were 30 degrees or less, but would overshoot a lot when the turn angles were larger. I would disconnect the Autopilot, follow the GPS's recommendation for a "STEEP TURN" onto the new course, and then connect the autopilot again.

So, all in all, a nice, relaxing flight.

End Date: September 14, 2002


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Copyright 2002, All Rights Reserved, Marc J. Zeitlin